This invention relates generally to computer numerical control systems for machine tools and more particularly to the graphical display of information related to the controlled tool and the machining process.
Numerical control systems for controlling machine tools in accordance with the execution of a digital computer are well known. Such systems control the machining operation in response to one or more part programs which are stored in a memory after having been loaded into the memory by punched tape, for example. Upon demand, the part program directs the machine through a series of fabrication steps. Where, for example, the machine includes a cutting tool, the relative motion between the workpiece and the cutting tool is normally along three mutually perpendicular axes to make a series of straight line or circular cuts in accordance with the part program which dictates the cutting tool motion. Additionally, a computer numerical control (CNC) system may be adapted to control other functions such as tool changes, spindle speed, coolant flow, pallet selection and video graphics and message generation. The number and type of functions vary considerably depending upon the type of machine tool being controlled. In the past, control has been performed by dedicated hardwired circuits which operate in response to sensed conditions on the machine tool and to commands in the part program. More recently, however, the logic associated with machine tool control systems has been implemented in a computerized system by means of a set of stored programs, (i.e., software) to provide the overall control. The software is tailored for a particular application but may be readily modified as required to meet specific needs. The addition of programmable control to a numerical control system provides a number of advantages, the first and foremost is that it is only necessary to reprogram the control to enable it to interface with a particular machine. Additionally, it is relatively easier for the user to program because of the type of instruction set which is employed and the editing features which are available.
A computerized numerical control may include two separate sets of software, namely, the "numerical control logic", termed the NC software, which is more or less fixed in content, and the "machine control logic" termed the MCL program, which is flexible and adaptable for customization to a particular machine tool. In the industry, customization is usually carried out by an original equipment manufacturer (OEM). The NC software controls part making, movement of axes, message display and other auxiliary functions while the MCL program primarily, if not exclusively, controls operation of the machine tool. In the above mentioned application, "Customization Window For A Numerical Control System", there is disclosed, moreover, a software interface, i.e., the customization window, which is comprised of a group of programs, input/output arrays, and status flags that link the NC software, the MCL program and the machine tool. In the related application, "Graphics Display Generation Method For A Numerical Control System", there is disclosed a method implemented in the MCL program for generating graphic displays when a machine tool operator, for example, requests the display of machine status information. A graphic display is provided which is dynamically updated on a periodic basis.
For visually displaying information, both graphic and textual, related to the machine tool and the machining process, a video display unit (cathode ray, CRT) is usually provided. The visual display enables a quick perception, for example, of the machine status. Adding color to the visual display further enhances the effect. A problem with color, however, is that human perception of different colors is variable. What may be a stark contrast for one operator may be essentially no contrast for another. Thus, when the manufacturer of an NC system builds in, and fixes, the display colors, those colors will not in every case be the most effective.